Use vfs::FileSystem in ASTUnit when creating CompilerInvocation.

[ilya-biryukov]

Summary

It used to always call into the RealFileSystem before.

[klimek]

LG

[bruno]

Any reason why this doesn't contain a testcase?

[ilya-biryukov]

@bruno, I've added a test to clangd, see D34755.

include/clang/Frontend/Utils.h

 createChainedIncludesSource(CompilerInstance &CI,
                             IntrusiveRefCntPtr<ExternalSemaSource> &Reader);
 
 /// createInvocationFromCommandLine - Construct a compiler invocation object for
 /// a command line argument vector.
 ///
 /// \return A CompilerInvocation, or 0 if none was built for the given
 /// argument vector.
-std::unique_ptr<CompilerInvocation>
-createInvocationFromCommandLine(ArrayRef<const char *> Args,
-                                IntrusiveRefCntPtr<DiagnosticsEngine> Diags =
-                                    IntrusiveRefCntPtr<DiagnosticsEngine>());
+std::unique_ptr<CompilerInvocation> createInvocationFromCommandLine(
+    ArrayRef<const char *> Args,
+        IntrusiveRefCntPtr<DiagnosticsEngine>(),
+    IntrusiveRefCntPtr<vfs::FileSystem> VFS = nullptr);
 
 /// Return the value of the last argument as an integer, or a default. If Diags
 /// is non-null, emits an error if the argument is given, but non-integral.
 int getLastArgIntValue(const llvm::opt::ArgList &Args,
                        llvm::opt::OptSpecifier Id, int Default,
                        DiagnosticsEngine *Diags = nullptr);
 
 inline int getLastArgIntValue(const llvm::opt::ArgList &Args,

lib/Frontend/ASTUnit.cpp

ASTUnit *ASTUnit::LoadFromCommandLine(
   std::shared_ptr<CompilerInvocation> CI;
 
   {
 
     CaptureDroppedDiagnostics Capture(CaptureDiagnostics, *Diags,
                                       &StoredDiagnostics, nullptr);
 
     CI = clang::createInvocationFromCommandLine(
-        llvm::makeArrayRef(ArgBegin, ArgEnd), Diags);
+        llvm::makeArrayRef(ArgBegin, ArgEnd), Diags, VFS);
     if (!CI)
       return nullptr;
   }
 
   // Override any files that need remapping
   for (const auto &RemappedFile : RemappedFiles) {
     CI->getPreprocessorOpts().addRemappedFile(RemappedFile.first,
                                               RemappedFile.second);

lib/Frontend/CreateInvocationFromCommandLine.cpp

 using namespace llvm::opt;
 
 /// createInvocationFromCommandLine - Construct a compiler invocation object for
 /// a command line argument vector.
 ///
 /// \return A CompilerInvocation, or 0 if none was built for the given
 /// argument vector.
 std::unique_ptr<CompilerInvocation> clang::createInvocationFromCommandLine(
-    ArrayRef<const char *> ArgList,
-    IntrusiveRefCntPtr<DiagnosticsEngine> Diags) {
+    ArrayRef<const char *> ArgList, IntrusiveRefCntPtr<DiagnosticsEngine> Diags,
+    IntrusiveRefCntPtr<vfs::FileSystem> VFS) {
   if (!Diags.get()) {
     // No diagnostics engine was provided, so create our own diagnostics object
     // with the default options.
     Diags = CompilerInstance::createDiagnostics(new DiagnosticOptions);
   }
 
   SmallVector<const char *, 16> Args(ArgList.begin(), ArgList.end());
 
   // FIXME: Find a cleaner way to force the driver into restricted modes.
   Args.push_back("-fsyntax-only");
 
   // FIXME: We shouldn't have to pass in the path info.
   driver::Driver TheDriver(Args[0], llvm::sys::getDefaultTargetTriple(),
-                           *Diags);
+                           *Diags, VFS);
 
   // Don't check that inputs exist, they may have been remapped.
   TheDriver.setCheckInputsExist(false);
 
   std::unique_ptr<driver::Compilation> C(TheDriver.BuildCompilation(Args));
   if (!C)
     return nullptr;